server.js

const mongoose = require('mongoose');
const dotenv = require('dotenv');

dotenv.config({ path: './config.env' });
const app = require('./app');

// console.log(process.env);

const DB = process.env.DATABASE.replace(
    '<password>',
    process.env.DATABASE_PASSWORD
);

mongoose
    .connect(DB, {
        useUnifiedTopology: true,
        useNewUrlParser: true,
        useCreateIndex: true,
        useFindAndModify: false,
    })
    .then(() => {
        console.log('DB connection successful!');
    });

// start server
const port = process.env.PORT || 3000;
const server = app.listen(port, () => {
    console.log(`App running on port:${port}...`);
});

// this is how we handle unhandled rejection globally caused due to any process like db connection failed or any other process; process.listen if encountered any error then it will be catch to process.on();

process.on('unhandledRejection', (err) => {
    console.log(err.name, err.message);
    console.log('UNHANDLED REJECTION! Shutting down...');
    server.close(() => {
        process.exit(1);
    });
});